1. Field of the Invention
The present invention relates to a process for fixing highly volatile or non-volatile water soluble and/or water emulsifiable materials into a carrier matrix to impart a stable free flowing particulate form thereto.
2. Summary of the Prior Art
There has been a considerable effort in the past directed toward achieving the reduction of a variety of materials to a sensibly dry condition for purposes of convenience and/or stability during merchandising. Such efforts have concentrated heavily in the food, drug, and cosmetic industry where many natural and synthetic materials (referred to herein as fixable agents) which are employed for their aroma, flavoring, or medicinal properties are required to be placed in a particulate powder configuration. The problems encountered in achieving these goals are caused primarily by one or more of a number of properties possessed by these fixable agents such as high volatility, chemical instability, and toxic nature when inhaled. For example, many aroma and flavoring agents typically employed in food products are known to rapidly deteriorate upon exposure to the atmosphere, particularly at elevated temperatures. Moreover, those agents which are highly volatile are difficult to capture in solid form without a substantial loss at great economic cost when processed at elevated temperatures.
The methods which have been employed in the past to impart a powdered configuration to fixable agents include a variety of techniques such as plating, spray-drying, crystal occlusion, freeze drying, as well as a variety of other miscellaneous techniques.
Many of the above described techniques are similar in that they employ a carrier or diluent which serves as a solid powder matrix material onto or into which the fixable agent is applied or incorporated. Commonly employed carriers include a wide variety of gums, starches, sugars, starch hydrolysates and the like which are specific to each technique. The process conditions employed for each technique, however, play a significant role in determining the properties of the resulting fixed powder and are often associated with their own particular processing disadvantages.
For example, in a typical spray-drying operation a fixable material such as a flavoring agent, and a suitable carrier are dissolved or dispersed in water and then sprayed into an evaporative atmosphere using large quantities of air at elevated temperature.
A significant drawback in the spray-drying of flavors and odorants has been the required use of heat and expensive equipment in its production. The fugacity of certain nuances necessary in the "fresh" quality of fruit flavors or perfumes is particularly a problem in the standard spray-drying techniques. The heat necessary to effect the drying encapsulation is the primary cause of the loss of these highly important flavor and odor volatiles. In flavors and odorants, the lost volatiles are usually compensated for by increased addition of these components to the basic oil used in the emulsion destined for spray-drying. In some cases the balance may be restored, but the heat involved accelerates many other undesirable reactions within the flavor or odorant compound. These reactions involve oxidation, acetal formation, etc. Moreover, the large volumes of air which are employed in spray-drying require costly and time consuming purification procedures to avoid pollution problems if the fixable material which is evaporated during spray-drying is an irritant when inhaled, such as mustard oil.
Representative patents which illustrate various carriers and fixable agents include U.S. Pat. Nos. 3,314,803; 3,736,149; 3,786,159; 3,821,436; and 4,059,706.
In the crystal occlusion technique the carrier and fixable material are added to water to form a saturated solution of the carrier. The carrier is then allowed to crystalize from the solution and the fixable material is trapped as an impurity within the crystals. The crystal occlusion technique typically can only achieve low fixation levels of less than about 1% and often requires costly procedures for handling the saturated solution to prevent premature crystallization.
Representative patents which illustrate the crystal inclusion technique include U.S. Pat. Nos. 3,767,430; 3,787,592; 3,843,822; and 3,889,008.
The freeze drying technique as illustrated by U.S. Pat. No. 3,660,115 can incorporate the fixable material into a carrier at room temperature but requires expensive and sophisticated equipment to do so. Moreover, the carrier matrix material having the fixable material incorporated therein is extremely porous and requires the application of a film forming material to seal the entrances to the interstices of the carrier-powder particles. This is necessary to insure protection of the trapped or sorbed fixable material from undesirable exposure to the atmosphere which can cause degradation and volatilization thereof. The additional coating step has obvious economic disadvantages.
A number of techniques rely on certain types of sorption phenomona. For example, U.S. Pat. No. 3,903,295 employs a method wherein the fixable material is incorporated into a viscid medium. The viscid medium is then dispersed to form tacky particles which are sprayed into a bed of powdered carrier particles. Because of the tacky nature of the particles containing the fixable materials the carrier particles coat the surface of the tacky particles. In order to achieve tacky consistency the amount of liquid in the particles must be kept to a minimum. Moreover, it is not required that the viscid medium be water. Other materials, such as mineral oil, and the like can be employed. Consequently, there is a complete lack of recognition of the essential function performed by water in the context of the present invention. In order to form the tacky particles it is necessary to spray the viscid medium under a high pressure. The equipment and energy cost of spraying a highly viscous material possesses obvious economic disadvantages.
U.S. Pat. No. 3,956,511 also relies on one or more sorption phenomenon. The process disclosed therein employs an expanded dextrin as a carrier having a particularly defined bulk density. An expensive and time consuming process is required to expand the bulk density of the carrier material. The fixable material is an aqueous alcohol solution which can contain a maximum of 20% water. Further additional fixable materials can be dissolved into either the alcohol or water components of the aqueous alcohol solution and the solution is mixed with the expanded dextrin particles. Because of the high capillary surface area and porous nature of the expanded dextrin particles their contact with the aqueous alcohol solution induces adsorption and/or absorption of the solution. The primary disadvantage of these porous residues is the fact that the surface of the resulting fixed powdered particles are not sealed against the atmosphere and must therefore be stored in a hermetically sealed package to avoid loss of the volatile constituents present therein. Moreover, since a minimum amount of water is employed in the aqueous alcohol solution the dissolution phenomenon which is believed to operate in the practice of the present invention does not appear to occur.
U.S. Pat. No. 4,022,924 discloses a process wherein a liquid acid is co-dried with a soluble carbohydrate. In one embodiment when the liquid acid is sprayed onto bulk dextrin particles the acid is absorbed on the surface of these particles. Thus, it appears that only the surface of the particles are plated with the liquid acid in this embodiment. Moreover, since concentrated acids are employed, the amount of water present therein, if any, would appear to be kept to a minimum as evidenced by the low water of hydration present in phosphate salts which are used in conjunction with the liquid acids.
U.S. Pat. No. 1,930,527 employs large gum granules rather than powdered particles as a carrier. A water solution containing a fixable material is applied to the surface of agitated gum granules as a spray or mist. When the water solution strikes the surfaces of the granules a thin film of gum solution is formed on the surface thereof and the fixable material penetrates to the center of each granule without dissolving the same. The thin film of gum solution causes the gum granule to stick together. The adherence of the gum granules is acceptable in the context of this patent since a continuous sheet of bound gum granules is desired. However, in the context of the present invention a free flowing powder is desired and this process is incapable of achieving this goal. Moreover, the amount of water which contacts the gum granules is actually restricted to prevent the gum granules from going into solution.
U.S. Pat. No. 2,088,622 discloses a process which relies on the phenomenon of dehydration. More specifically, a fixable material and volatility reducent are emulsified and a dehydrating agent, such as a hygroscopic carbohydrate (e.g., corn starch), is added to the emulsion. The dehydrating agent absorbs water from the water phase of the emulsion and yields a dry material characterized by having a protective film about the emulsoid. This patent lacks any specific process details relating the drying step with a dehydrating agent, such as the particle size of the dehydrating agent, the method of application of the dehydrating agent to the emulsion, or even the configuration of the resulting fixed material. Consequently, there is nothing to suggest that a minimum amount of water must be present in the emulsion in order for the dissolution phenomenon to operate in the manner described in the present invention. Likewise, there is no suggestion that the emulsion must be added to the carrier in controlled amounts to achieve fixation in the manner described herein. Furthermore, the use of highly hygroscopic materials as the dehydrating agent leads to the formation undesirably large clumps of materials.
Other miscellaneous fixation techniques are disclosed in U.S. Pat. Nos. 2,756,177; 3,922,354; and 3,950,549.
There has been a continuing search for efficient, economic methods for achieving fixation of a fixable material in a free flowing powder configuration which imparts extended chemical and physical stability thereto. The present invention is a result of this search.
It is therefore an object of the present invention to provide an economical and energy efficient process capable of encapsulating a variety of volatile and non-volatile natural and synthetic materials with a carrier material without the aid of heat and with an improved degree of safety.
These and other objects and features of the invention will become apparent from the claims and from the following description.